Need to reduce amount of load combinations

[bojoka4052]

This is a bridge with five different lanes (Sidewalk, Driving lane, Driving lane, Bike lane and sidewalk).

This is how my beam element model looks, each beam in the longitudinal direction (x-direction) represents a lane. Supports are all roller supports.

The loads I have that can be on or off are brake loads from when the car brakes, wear layer that can be on or off, people can be walking on one or two lanes, people can be biking, cars can be driving on none of the lanes or both lanes etc. This creates many possible load combinations. I was wondering if people could help me figure out what are the worst case possible load combinations that could occur, and what load combinations I can look away from as they most likely wont be too bad? The bridge is about 40-50 m long.

 

[ThomasH]

Hi

What code are you using for this? Different codes have different requirements. I know that the Eurocode in combination with some national annexes can be nasty.

You have two driving lanes and one bike lane. Are you sure that the bike lane shouldn't be designed for cars?. And I suspect the cars are not the only vehicles on the bridge?

Before going into the load combinations and how to reduce them I think we need a better description of the problem .

I suspect that the different lanes will have different governing load combinations. And there may be differenet combinations depending on what action you are checking.

Thomas

 

[MotorCity]

Based on your handle, you are mechanical. Are you familiar with bridge design? I ask because based on the nature of your questions, it sounds like you are working outside of your area. Sure, you may be able to eliminate some load combinations but in order to do that, you need to be familiar with the loads and load combinations, and have the experience to know what load combinations will or will not govern. I can tell you that there are several more loads that need to be considered in addition to those listed above, as well as other loads that may apply. The load combinations dictate what loads "can be on or off". 40m to 50m is a pretty healthy span (which is unusual that the span is only known within 10m). If you are using AASHTO (and I suspect other bridge codes may have similar parameters), the load combinations have parameters other than just the load factors. We cannot sort out the load combinations for you, but we can help if you have specific questions.

 

[centondollar]

You need to construct influence lines, either manually or by computer. Some FEA software, such as Sofistik, allow introduction of "moving loads" which - when combined with re-running analysis for each load location and creating an envelope of the solutions internally in the software - can find load combinations which create the most critical effects in the locations of greatest interest (e.g., mid-span and at supports) to the bridge engineer.

 

[rb1957]

what you're talking about is experience. We all have our own experience and it leads us to suggest things. You need your own experience, and not "I read it on the internet".

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

 

[JLNJ]

50 meter bridge? Hire a competent, experienced bridge engineer.